The present invention relates to absorbent structures particularly useful in absorbent hygienic articles, such as baby or adult incontinence diapers, hygienic feminine protection articles and the like.
Absorbent articles for receiving and retaining bodily discharges such as urine or feces such as disposable diapers, training pants, adult incontinence articles are well known in the art, and significant effort has been spent against improving their performance. The ability to provide better performing absorbent articles such as diapers has been contingent on the ability to develop relatively thin absorbent cores or structures that can acquire and store large quantities of discharged body fluids, in particular urine.
In this regard, the use of certain absorbent polymers often referred to as xe2x80x9chydrogels,xe2x80x9d xe2x80x9csuperabsorbentsxe2x80x9d or xe2x80x9chydrocolloidxe2x80x9d or xe2x80x9chydrogel formingxe2x80x9d material has been particularly important. See, for example, U.S. Pat. No. 3,699,103 (Harper et al), issued Jun. 13, 1972, and U.S. Pat. No. 3,770,731 (Harmon), issued Jun. 20, 1972, that disclose the use of such absorbent polymers (hereafter xe2x80x9chydrogel-forming absorbent polymersxe2x80x9d) in absorbent articles. Indeed, the development of thinner diapers has been the direct consequence of thinner absorbent cores that take advantage of the ability of these hydrogel-forming absorbent polymers to absorb large quantities of discharged body fluids, typically when used in combination with a fibrous matrix. See, for example, U.S. Pat. No. 4,673,402 (Weisman et al), issued Jun. 16, 1987 and U.S. Pat. No. 4,935,022 (Lash et al), issued Jun. 19, 1990, that disclose dual-layer core structures comprising a fibrous matrix and hydrogel-forming absorbent polymers useful in fashioning thin, compact, non-bulky diapers. See also, U.S. Pat. No. 5,562,646 (Goldman et al.), issued Oct. 8, 1996 and U.S. Pat. No. 5,599,335 (Goldman et al.), issued Feb. 4, 1997, both of which relate to absorbent cores comprising regions of high concentrations of hydrogel-forming polymer, where the polymer forms a gel-continuous fluid transportation zone upon swelling.
Also the application of such materials in absorbent structures and absorbent articles focused on storage of the fluids within the structure, often considering comfort aspects like thinness of the structure, such as disclosed U.S. Pat. No. 4,610,678 entitled xe2x80x9cHigh-Density Absorbent Structuresxe2x80x9d issued to Weisman et al. on Sep. 9, 1986; U.S. Pat. No. 4,673,402 entitled xe2x80x9cAbsorbent Articles With Dual-Layered Coresxe2x80x9d issued to Weisman et al. on Jun. 16, 1987; U.S. Pat. No. 4,888,231 entitled xe2x80x9cAbsorbent Core Having A Dusting Layerxe2x80x9d issued to Angstadt on Dec. 19, 1989; EP-A-0 640 330 of Bewick-Sonntag et al.; U.S. Pat. No. 5,180,622 (Berg et al.); U.S. Pat. No. 5,102,597 (Roe et al.); U.S. Pat. No. 5,387,207 (LaVon); EP-A-774.242; or EP-A-0.797.968 and EP-A-0.810.078.
With improved liquid handling properties of the absorbent members, their fluid retention and suction ability was increased by two mechanisms, namely the liquid suction of the absorbent materials (such as superabsorbent materials) per se on one side, and on the other side the possibility to use higher amounts and especially higher concentrations of such materials.
Especially with particulate superabsorbent material a further problem was identified, namely the containment of these particles within the absorbent memberxe2x80x94in the dry state as well as in the wet state.
Generally, conventional tissue wrap sheets are well known in the art to address this problem. In U.S. Pat. No. 5,458,592 (Abuto), thermoplastic fibrous non-woven core wrap webs are described, aiming at an improvement over paper tissues as well as over conventional nonwoven webs. The benefit over the latter is attributed to the smaller pore size of the described webs, which are exemplified as so-called melt-blown webs. Such webs are essentially made from hydrophobic base materials, such as polyolefins like polypropylene, or are made from other polymeric materials exhibiting an insufficient hydrophilicity. Therefore, surfactants are utilized to improve hydrophilicity, such as of the TRITON X-102 type, which readily washed out
However, the prior art, and especially the disclosure of U.S. Pat. No. 5,458,592 (Abuto), failed to recognize, with respect to the fluid handling properties, the interaction which occurs when non-woven core wraps are combined with modern fluid storage members, which have a strong liquid retention ability, and which are designed for uses with multiple gushes. Under such conditions, inventors have realized, that it is not only important that the core wrap non-wovens are sufficiently hydrophilic to allow wetting, but also that the non-wovens must be able to maintain their hydrophilicity for subsequent gushes.
The key effect which makes this an important requirement is the ability of the storage member to dry out the pores of the core wrap materials, such that upon receipt of the subsequent loading or gush, the web performs like a hydrophobic barrier. In case of storage members with a lower dewatering capability, such as the ones disclosed in U.S. Pat. No. 5,458,592 (Abuto), these do not dewater the small pore webs, such as can be achieved by small diameter fiber webs, such that there is still some residual liquid in the pores of the web such that upon rewetting the liquid can readily penetrate there through.
Henceforth, it is an object of the present invention to provide high suction absorbent structures with a melt-blown non-woven wrap sheet, comprising small diameter fibers, which do not have these drawbacks, and allow good liquid penetration over repeated gushes, without compromising on liquid retention.
The present invention is an absorbent structure with an ultimate fluid storage member, comprising superabsorbent material at a concentration of at least 40% of the total weight of said ultimate fluid storage member, preferably more than 50%, more preferably more than 60%, and in even more preferred executions more than 70% or even more than 90%, whereby the superabsorbent material has a Performance under pressure (PUP) value of at least 23 g/g, preferably 25 g/g, more preferably more than 29919, and a Saline Flow Conductivity (SFC) value of at least 30xc3x9710xe2x88x927 cm3 sec/g, preferably more than 50xc3x9710xe2x88x927 cm3 sec/g, even more preferably more than 100xc3x9710xe2x88x927 cm3 sec/g. Further, the absorbent structure comprises a non-woven wrap sheet comprising fibers having a diameter corresponding to less than 1.2 dTex, preferably less than 0.9 dTex, and even more preferably less than 0.7 dTex, which is in direct fluid communication with said storage member, and which has in the strike-through test as described hereinafter a strike-through time in the second load of less than 60 seconds, preferably less than 30 seconds, even more preferably of less than 10 seconds, and most preferably less than 5 seconds.
In the absorbent structure, the wrap sheet can completely envelope the absorbent member by being in direct contact with all of the six surfaces of the absorbent member, or only parts of the surface, such that the absorbent structure may also be in direct contact with the backsheet of the article. Also, the absorbent structure can comprise more than one wrap sheets.
The absorbent structure is particularly useful in absorbent articles, such as baby or adult incontinence diapers, optionally in combination with other fluid handling members, such as distribution or acquisition member.